Patent GB-1038536-A (GB)
Title: Refrigeration system
IPC: F25B47/02
Filed: 1964-05-15
Abstract: 1,038,536. Refrigerating; defrosting. L. K. QUICK. May 15, 1964, No. 20455/64. Heading F4H. In a compression-condensation refrigeration system having a plurality of evaporators means are provided for selectively conveying hot gaseous refrigerant from the compressor to any evaporator and for conveying the refrigerant used to defrost that evaporator to another evaporator for evaporation therein. As shown, the refrigeration system comprises compressors 210, 211, an air-cooled condenser 215, a watercooled condenser 232, a liquid line header 240, evaporators 241, 251 ... 291 and suction line headers 301 and 302. Valve controlled hot gas lines 247, 257 ... 297 lead from a header 311 to the outlets of the evaporators and lines 248, 258 . . . 298 serve to convey refrigerant used to defrost the evaporators from the inlet sides of the latter to a header 312. In the inlet lines 243, 253 ... 293 to the evaporation there are provided thermostatic expansion valves 244, 254 ... 294 and on-off valves 242, 252 ... 292 which are closed when the temperature in the fixture in which the associated evaporator is positioned reaches a predetermined low value, the lines 248 ... 298 being connected to the evaporator inlet lines between these valves. Valves 244 ... 294 are provided with by-pass lines 313 including check valves 314. In operation, evaporator 241, for example, is defrosted by opening valve 249 in line 247 and valve 250 in line 248 and closing a valve 246 downstream of the evaporator and valve 242 in the evaporator inlet line, refrigerant used in defrosting evaporator 241 being supplied to header 312 increasing the pressure therein. Valves 250, 260 ... 290 in lines 248 ... 298 are so constructed as to permit flow from the evaporators to the header 312 only when they are opened by a solenoid but to permit flow in the reverse direction when the pressure difference between the header and the evaporator reaches a predetermined value. Thus, when the pressure in an evaporator drops due to the closure of any of valves 242 ... 292 refrigerant from the header is forwarded to that evaporator for evaporation. Evaporator 271, however, is positioned in a fixture in which the temperature must not drop below a predetermined minimum and so a check valve 330 is provided in line 278 to prevent refrigerant from entering the evaporator when valve 272 is closed. If none of the valves 242 ... 292 is closed during defrosting of evaporator 241 a device 333 is arranged to close valves 252 and 262 in response to an increased pressure in header 312. The system includes an oil separator 213 with an associated receiver 221 from which refrigerant is returned to the system through line 222 and oil is returned to the compressors through lines 223 and 224 having float controlled valves 225 and 227 respectively. A cooler 218 between the compressor stages is cooled by the admission of refrigerant from liquid header 240 via an expansion valve 310. The defrosting operation is under time control. In a modification (Fig. 1, not shown) the header 312 is omitted and two evaporators are shown, the inlet lines of the evaporators being connected by two lines each of which includes an on-off valve and a check valve. Thus, refrigerant used in defrosting one evaporator can be passed to the inlet of the other by opening the appropriate on-off valve. An electric circuit for opening and closing the valves of the system under the control of timing means 3 and for energizing electric drain heaters is illustrated in Fig. 2 (not shown).